Developing device with structure to release inner pressure

Abstract

The developing device includes a developing roller, a developer conveying unit, a developer discharge unit, and an air discharge port. The developer conveying unit includes a developing chamber provided with the developing roller and extending in a longitudinal direction of the developing roller, a stirring chamber arranged in parallel to the developing chamber, and a barrier wall having a first communication port and a second communication port, at respective ends in the longitudinal direction, to connect the developing chamber with the stirring chamber. The developer discharge unit extends from the developer conveying unit in the longitudinal direction of the developing roller and includes a developer discharge port to discharge excess developer. The air discharge port is to house a filter to filter a developer, the air discharge port being provided between the developer conveying unit and the developer discharge unit to discharge air in the developer conveying unit.

What is claimed is: 
     
       1. A developing device comprising:
 a developing roller; 
 a developer conveying unit comprising a developing chamber provided with the developing roller and extending in a longitudinal direction of the developing roller, a stirring chamber arranged in parallel to the developing chamber, and a barrier wall having a first communication port and a second communication port, at respective ends in the longitudinal direction, to connect the developing chamber with the stirring chamber; 
 a developer discharge unit extending from the developer conveying unit in the longitudinal direction of the developing roller and including a developer discharge port to discharge excess developer; and 
 an air discharge port to house a filter to filter a developer, the air discharge port being provided between the developer conveying unit and the developer discharge unit to discharge air in the developer conveying unit. 
 
     
     
       2. The developing device of  claim 1 , further comprising:
 an internal circulation path provided between the developer conveying unit and the developer discharge unit and connecting the developing chamber to the stirring chamber to form an air passage. 
 
     
     
       3. The developing device of  claim 2 , wherein the internal circulation path includes a first connection opening and a second connection opening connected to the developing chamber and the stirring chamber, respectively,
 wherein the first connection opening is connected to a downstream side of the developing chamber with reference to a flow direction of the developer in the developing chamber, and 
 the second connection opening is connected to an upstream side of the stirring chamber with reference to a flow direction of the developer in the stirring chamber. 
 
     
     
       4. The developing device of  claim 3 , wherein the second connection opening is to open in the flow direction of the developer in the stirring chamber. 
     
     
       5. The developing device of  claim 3 , wherein the developer discharge unit extends from the downstream side of the developing chamber with reference to the flow direction of the developer in the developing chamber. 
     
     
       6. The developing device of  claim 2 , wherein the air discharge port is to open in a circulation path forming housing forming the internal circulation path. 
     
     
       7. The developing device of  claim 2 , wherein the air discharge port extends beyond the internal circulation path toward the developer discharge unit and is inclined in the longitudinal direction. 
     
     
       8. The developing device of  claim 2 , wherein the air discharge port comprises a first air discharge port extending beyond the internal circulation path and toward the developer discharge unit and is inclined in the longitudinal direction and a second air discharge port to open in an outer wall forming the internal circulation path, and
 the filter comprises first and second filters located in the first and second air discharge ports, respectively. 
 
     
     
       9. A developing device comprising:
 a developing roller; 
 a developer conveying unit comprising a developing chamber provided with the developing roller and extending in a longitudinal direction of the developing roller, a stirring chamber arranged in parallel to the developing chamber, and a barrier wall having a first communication port and a second communication port, at respective ends in the longitudinal direction, to connect the developing chamber with the stirring chamber; 
 a first conveying member located in the developing chamber to convey a developer from the second communication port in a first direction; 
 a second conveying member located in the stirring chamber to convey a developer from the first communication port in a second direction opposite to the first direction; 
 a developer discharge unit extending from the developing chamber in the first direction and including a developer discharge port to discharge excess developer; and 
 an air discharge port to house a filter to filter a developer, the air discharge port being provided between the first communication port and the developer discharge unit to discharge air in the developer conveying unit. 
 
     
     
       10. The developing device of  claim 9 , further comprising:
 an internal circulation path provided between the first communication port and the developer discharge unit and connecting the developing chamber to the stirring chamber to form an air passage. 
 
     
     
       11. The developing device of  claim 10 , wherein the internal circulation path includes a first connection opening and a second connection opening connected to the developing chamber and the stirring chamber, respectively,
 wherein the first connection opening is between the first communication port and the developer discharge port, and 
 the second connection opening is between the second communication port and a supply port. 
 
     
     
       12. The developing device of  claim 11 , wherein the second connection opening is to open in the second direction. 
     
     
       13. The developing device of  claim 10 , wherein the air discharge port is to open in a circulation path forming housing forming the internal circulation path. 
     
     
       14. The developing device of  claim 10 , wherein the air discharge port extends beyond the internal circulation path and toward the developer discharge unit and is inclined in the longitudinal direction. 
     
     
       15. The developing device of  claim 10 , wherein the air discharge port comprises a first air discharge port extending beyond the internal circulation path and toward the developer discharge unit and is inclined in the longitudinal direction and a second air discharge port to open in an outer wall forming the internal circulation path, and
 the filter comprises first and second filters located in the first and second air discharge ports, respectively.